{
语法百题 解题报告：
 http://git.oschina.net/et0662/sznoi-grammar/ 
}
var
	n:integer;
begin
	readln(n);
	if n<=6 then
		writeln(3)
	else if n<=16 then
		writeln(4)
	else if n<=26 then
		writeln(5)
	else
		writeln(6);
end.
